Mobile cranes are already known in which the counterweight arrangement is disposed movably to the superstructure in order to increase or decrease the counter-torque. Thus, for example, a mobile crane is specified in DE 10 2012 006 494 B4, in which the counterweight arrangement can be shifted in linear fashion along the lengthwise axis of the superstructure in order to increase or decrease the counter-torque. The position of the counterweight arrangement can be adapted mechanically to the tilt angle of the jib by a coupling mechanism, which can also be optionally decoupled once again.
A counterweight arrangement which is arranged movably on the superstructure is known from CN 102229415 B, which can be moved in linear manner along the superstructure via corresponding piston and cylinder arrangements to increase or decrease the counter-torque.
If, now, the counterweight arrangement is shifted backward by the corresponding piston and cylinder arrangement of the coupling rod to increase the counter-torque, the swivel radius of the superstructure automatically increases. At construction sites with narrow space available, this can cause problems with interfering edges, such as those of building walls or other interfering structures.
The problem which the present invention proposes to solve is to modify a mobile crane of the mentioned kind so that the ballast radius can be adjusted in easy manner over the largest possible adjustment path, while at the same time the swivel radius of the superstructure is minimized as much as possible.
According to the invention, this problem is solved by a mobile crane with a drivable undercarriage and a rotatable superstructure mounted thereon, where on the one side there is pivoted a swiveling jib, and on the other side a counterweight arrangement is mounted which is movable relative to the superstructure. According to the invention, the counterweight arrangement has a counterweight base plate, on which at least two stacks of counterweights are arranged and able to swivel about a vertical axis. Thanks to the new concept of swiveling capability of the stack of counterweights, an easy adjustment of the ballast radius is possible by rotary movement, thereby achieving a large adjustment path.
Advantageous configurations of the invention will appear from the subsidiary claims connected to the main claim.
Accordingly, the counterweight base plate can be joined by a counterweight frame to the superstructure. This makes it possible to separate the entire counterweight arrangement when needed in easy fashion from the superstructure, for example, in order to be driven on its own transport vehicle during road traffic in order to decrease the base weight of the mobile crane.
According to another advantageous embodiment of the invention, the stacks of counterweights can be placed on swivel arms pivoting on the counterweight base plate, which can swivel continuously from a maximum retracted to a maximum extended position via swivel drive units, for example in the form of hydraulically operated piston and cylinder arrangements or electrically operated adjusting means. Such a swivel drive unit is necessary, since the bearing forces in the vertical swivel bearing are very large.
Especially advantageously, the counterweight plates which can be formed into the stacks of counterweights can have an essentially triangular shape. This makes it possible for the center of gravity of the movable parts of the counterweight arrangement to move further away from the axis of rotation of the superstructure about the undercarriage than the outermost point of the counterweight arrangement. Thus, the outermost point of the counterweight arrangement, forming the swivel radius of the superstructure and determining the space needed at the construction site, is increased less than the outwardly moved swivel point of the movable parts of the counterweight arrangement to generate the larger counter-torque.
Advantageously, the swivel angle of the swivel arms can be detected by sensors. Thus, the position of the swivel arms can be provided to the control unit. This is therefore able to take into account intermediate positions as well in the crane monitoring.
The adjustable ballast radius means in particular that the superstructure can rotate by 360° within the support base for a small ballast radius. It is of special benefit when the corresponding sensor signals can be fed to a corresponding crane controller which can carry out a method for the monitoring of crane safety in accordance with DE 10 2012 011 871 A1. Since the mobile crane can be set up with any desired support base, it can be operated close to interference edges at narrow construction sites, such as the walls of houses. Thanks to the swivel mechanism according to the invention, the counterweight base plates of the counterweight arrangement can be adjusted in very easy manner, so that the radius of turning of the superstructure can be adapted in easy manner to the interference edges.
If a very large counter-torque is needed, so that the stacks of counterweights would become too high, according to an especially advantageous configuration in the context of the invention one can also provide four stacks of counterweights, which are arranged to swivel about four vertical axes. In this way, the bearing forces on the vertical bearings can be lowered. Preferably, the two stacks of counterweights arranged alongside each other can be pivoted and coupled together, resulting in a kind of parallelogram guidance.
According to another advantageous embodiment of the invention, the counterweight arrangement consisting of the counterweight frame, the counterweight base plate, the swivel arms pivoting on the latter and optionally winch with cable and reeved pulley case laid down on the counterweight frame can be removed as a whole from the superstructure as a self-standing transport unit. This transport unit can then be loaded onto a semi truck provided especially for this for its transport. Especially advantageously, at least one counterweight plate is already placed on the counterweight arrangement for the transport. This then facilitates the assembly of the mobile crane, since the counterweight arrangement is already assembled with counterweight plate placed on the superstructure.
According to one alternative advantageous embodiment, in the case when the counterweight arrangement remains on the superstructure during the road transport, a base plate arranged on the swivel arms to receive the counterweight plates can be taken off and fastened on the mobile crane. This alternative embodiment is designed for mobile cranes which can travel with substantially greater axle loads in public road traffic than is the case in Germany. The counterweight arrangement can remain on the superstructure here. Now, in order to distribute the axle load as evenly as possible during the road trip, the base plates are designed to be separated from the counterweight arrangement. They are taken up accordingly by transport receptacles provided on the mobile crane. Advantageously, these transport receptacles are provided in the region of the heavily dimensioned areas of the sliding beam box on the undercarriage of the mobile crane.
Advantageously, the stacks of counterweights can be adjusted at different counterweight radius, i.e., one tower stands at 7 m outer radius, for example, the other at 5 m outer radius. Since each stack of counterweights has its own swivel arm, this independent adjustment is possible.
Other features, details and benefits of the invention will be explained more closely with the help of the sample embodiments represented in the Figs.